How does rising atmospheric CO2 affect marine organisms?

Click to locate material archived on our website by topic

A Holocene Temperature History of Canada's Devon Island

Paper Reviewed
Courtney Mustaphi, C.J. and Gajewski, K. 2013. Holocene sediments from a coastal lake on northern Devon island, Nunavut, Canada. Canadian Journal of Earth Science 50: 564-575.

In setting the stage for their important lake sediment study, the authors write that "laminated sediments, composed of undisturbed, very fine depositional beds, are one type of high-resolution archive of past environmental and climatic variability." And they say that "if the laminae are deposited annually, i.e., varves, these can provide a precise chronological control on the resulting paleoenvironmental reconstruction."

In the case of their particular study, Courtney Mustaphi and Gajewski report on their analysis of Holocene sediments collected from a small coastal lake, DV09 (Gajewski et al., 1997), located on northern Devon Island, Nunavut, which is a region of Canada where few lake sediment records have been analyzed in detail. And, therefore, the purpose of their paper, as they describe it, was to "interpret the post-glacial ontogeny of the lake system through sediment analyses performed on a long core."

Knowing that "the uppermost sediments contained very fine, discrete, and continuous laminae that were shown to be annually deposited, i.e., varved, over the recent past (~150 years; Gajewski et al., 1997)," plus the fact that "subsequent studies have independently confirmed the annual nature of the uppermost laminae through 210Pb dating of short cores from the lake (Outridge et al., 2002, 2005, 2007; Stern et al., 2005)," Courtney Mustaphi and Gajewski went on to construct a varve chronology of the last 1600 years, after which they analyzed the paleoenvironmental significance of the laminated deposit. And in doing so, they found that the low-frequency variability of the site "was qualitatively coherent with many other High Arctic hydroclimatic paleorecords from the Canadian Archipelago, as well as regional and hemispheric temperature reconstructions."

As for the significance of their findings, the two Canadian researchers write that "sediment deposition into DV09 was highest during warmer periods, such as the Holocene Thermal Maximum and MCA [Medieval Climate Anomaly = Medieval Warm Period (MWP)]." And knowing that the Holocene Thermal Maximum was the warmest period of the entire current interglacial, one can validly surmise that the MWP - being listed as a warm climate interval right beside it - must rank right up there among the very top tier of Holocene "hot times," during an era when the atmosphere's CO2 concentration was something on the order of only 280 ppm, which clearly implies that the lesser warming of today - see our Medieval Warm Period Project - need not be due to the fact that the air's CO2 concentration now stands at about 400 ppm.

Gajewski, K., Hamilton, P.B. and McNeely, R. 1997. A high resolution proxy-climate record from an arctic lake with annually-laminated sediments on Devon Island, Nunavut, Canada. Journal of Paleolimnology 17: 215-225.

Outridge, P.M., Hermanson, M.H. and Lockhart, W.L. 2002. Regional variations in atmospheric deposition and sources of anthropogenic lead in lake sediments across the Canadian Arctic. Geochimica et Cosmochimica Acta 66: 3521-3531.

Outridge, P.M., Stern, G.A., Hamilton, P.B., Percival, J.B., McNeely, R. and Lockhart, L.W. 2005. Trace metal profiles in the varved sediment of an Arctic lake. Geochimica et Cosmochimica Acta 69: 4881-4894.

Outridge, P.M., Sanei, H., Stern, G.A., Hamilton, P.B. and Goodarzi, F. 2007. Evidence for control of mercury accumulation rates in Canadian High Arctic lake sediments by variations of aquatic primary productivity. Environmental Science and Technology 41: 5259-5265.

Stern, G.A., Brackevelt, E., Helm, P.A., bidleman, T.F., Outridge, P.M., Lockhart, W.L., McNeeley, R., Rosenberg, B., Ikonomou, M.G., Hamilton, P., Tomy, G.T. and Wilkinson, P. 2005. Modern and historical fluxes of halogenated organic contaminants to a lake in the Canadian arctic, as determined from annually laminated sediment cores. Science of the Total Environment 342: 223-243.

Posted 28 October 2014